Fourier-transform (FT) Raman spectroscopic methods, using near infrared laser excitation, was developed for examining membrane related systems not amenable to conventional dispersive Raman techniques. The effects of macrolide polyene antibiotics, amphotericin A and amphotericin B (possible AIDS therapeutic agents) on model membrane systems were investigated using FT-Raman spectroscopic procedures. The two polyene antibiotics introduce interdigitated lipid phases in both cholesterol free and cholesterol containing membranes. The structural defects originating within the membrane from interdigitated lipid domains may be a critical factor in reducing HIV virion infectivity.